1. Field of the Invention
The field of art to which this invention pertains is solid-bed adsorptive separation. More specifically, the invention relates to an improved adsorbent, method of manufacture of the adsorbent and process for separating a component from a mixture comprising an aqueous solution of a mixture of different components using the adsorbent, the adsorbent comprising a crystalline aluminosilicate and cationic exchange resin dispersed in a water permeable organic polymer binder material and having the capability of selectively adsorbing a component from the feed mixture.
2. Prior Art
It is known in the separation art that certain crystalline aluminosilicates referred to as zeolites can be used in the separation of a component from an aqueous solution of a mixture of different components. For example, adsorbents comprising crystalline aluminosilicate are used in the method described in U.S. Pat. No. 4,014,711 to separate fructose for a mixture of sugars in aqueous solution including fructose and glucose.
It is also known that crystalline aluminosilicates or zeolites are used in adsorption processing in the form of agglomerates having high physical strength and attrition resistance. Methods for forming the crystalline powders into such agglomerates include the addition of an inorganic binder, generally a clay comprising silicon dioxide and aluminum oxide, to the high purity zeolite powder in wet mixture. The blended clay zeolite mixture is extruded into cylindrical type pellets or formed into beads which are subsequently calcined in order to convert the clay to an amorphous binder of considerable mechanical strength. As binders, clays of the kaolin type are generally used.
Organic polymer binders are also known to the art.
Zeolite crystal and inorganic binder agglomerates have long been known to have the property of gradually disintegrating as a result of continuous contact with water. This disintegration has been observed as a silicon presence or contamination in the solution in contact with the adsorbent. Such contamination may at times be sufficiently severe to impart a cloudy appearance to the solution.
It is known in the separation art that certain ion (i.e. cation) exchange resins can be used in separating components from a fluid mixture, particularly a saccharide from an aqueous solution of saccharides. Examples of such art are U.S. Pat. Nos. 4,025,357; 4,022,637; 3,928,193; 3,817,787; 3,806,363; 3,692,582; 3,416,961; 3,184,334; 3,174,876; 3,044,906; 3,044,904; and 2,813,810. Common ion exchange resins used in the prior art processes are alkali metal and alkaline earth metal salts of a polystyrene sulfonate cation exchange resin cross-coupled with divinyl benzene. The art recognizes a tendency of such resins to expand or contract in volume, depending on the ionic strength of the aqueous medium in which they are placed. When the resin is used for separating components from an aqueous stream by passing the stream through a column packed with the resin as an adsorbent, such tendency results in a lack of packing uniformity and homogeneity of resin particle size which in turn causes extreme variance, i.e. rise, in the pressure drop through the column.
We have discovered an improved adsorbent comprising a mixture of crystalline aluminosilicate and cation exchange resin dispersed in a water permeable organic polymer binder, a method of manufacturing the adsorbent and an improvement to an aqueous separation process which minimizes the disintegration of the adsorbent and silicon contamination of the product as well as the aforementioned problems inherent in the tendency of the resin to change volume.